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VDI solved a seemingly simple problem. Users were having a hard time processing and printing out loan packages fast enough. Using a standard-issue desktop, the process took 15 minutes, but the credit union wanted its representatives to process six loan applications per hour.

Barlow isn't a big fan of Microsoft Terminal Services or Citrix Presentation Server, so he wanted to avoid going down that road. Because it runs on top of a Windows operating system, Citrix can't assign much more than 3 GB of system memory to end users, limiting the number of users you can host per system, Barlow explained. And not all applications work well under Citrix. "Citrix always seemed like a kludge to me. You have to make applications work in Citrix – and they don't always."

The loan printing process decreased from 15 minutes to 45 seconds without requiring any changes to the application.,

Virginia Credit Union was already running VMware ESX Server to host back-end server applications, so Barlow decided to try and encapsulate a standard desktop image in a Windows XP virtual machine (VM) to see how it would perform. To his surprise, the loan printing process decreased from 15 minutes to 45 seconds without requiring any changes to the application.

Why the loan printing process was so much faster with a VDI client isn't perfectly clear. "I think that [the agents] were just too far from the data," Barlow hypothesized. Whatever the case, "once users saw how cool this was, they started demanding it." Barlow said. Thanks to this VDI workaround, the credit union has avoided having to hire two people, he said.

On a whim, Barlow decided to try out the A-SIS data deduplication feature that NetApp had thrown in with the credit union's FAS6070 storage system to see if it would shrink the data footprint of VDI clients. To Barlow's surprise, running A-SIS dedupe on the 20 VMs' 400 GB NFS volume brought the data storage requirement down to a mere 19 GB. Since that initial deduplication process, the storage capacity consumed by those VDI clients tends to hover around 25 GB – still a savings of more than 90%.

Barlow has reduced the storage capacity consumed by his VDI environment even further by using another feature of NetApp's Data Ontap 7 G operating environment called FlexClone . Barlow uses it to create a snapshot-based clone of the base Windows XP desktop image that uses up no storage capacity until users begin to make changes to it.

Barlow now uses A-SIS to deduplicate most of his storage environment, and sees large space savings across non-VDI environments as well. A-SIS saves generic servers between 40% to 60% storage, and CIFS/NFS servers shrink by 50% to 60%. Now his rule is this: "If it's not a LUN [logical unit number], we dedupe it," he said. Deduping LUNs does result in storage savings, but they aren't necessarily recognized by the application on the other side, causing confusion.

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Dedupe's lunatic fringe Virginia Credit Union's use of deduplication on primary storage is cutting edge, said Steve Norall, senior analyst with Taneja Group, an analyst firm in Hopkinton, Mass. "In general, the dedupe phenomenon has mainly been relegated to backup and archiving," as exemplified by products from vendors like Data Domain, FalconStor Software and Sepaton. At the same time, a new crop of startups focused on dedupe for primary storage has emerged, Norall said -- companies like Storwize and Ocarina Networks. But deduplicating VDI clients is a great idea, said Tony Asaro, senior analyst at Enterprise Strategy Group in Milford, Mass. "Those images have a lot of duplicate data in them," he said.

But NetApp's brand of deduplication is a performance-intensive process that should be scheduled carefully, Asaro said. When it comes to a storage subsystem, "there could be a lot of things going on at once: a RAID rebuild, data replication, etc. Then you throw dedupe on top of it, and you don't know what could happen."

Virginia Credit Union has the luxury of running A-SIS on NetApp's top-of-the-line FAS6070, so performance hasn't been a problem, Barlow reported. "We tweaked the schedule for when it runs a bit, but the box is so powerful that users don't even see a difference."

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